1. Field of the Invention
The present invention relates to a method of fabricating a glass substrate for a magnetic disk which is used as a hard disk and a method of fabricating a magnetic disk.
2. Description of the Related Arts
An aluminum substrate is conventionally often used as a substrate for a magnetic disk. In association with demands of reduction in size and thickness of the magnetic disk and lower floating of a magnetic head, the ratio of using a glass substrate is being increased since the reduction in size and thickness of the glass substrate is easier, flatness is higher, the floating of the magnetic head is lower, and the like as compared with the aluminum substrate.
When the glass substrate is used as a substrate for a magnetic disk, a chemical strengthening treatment by a low-temperature ion exchange is generally performed to the surface of the glass substrate in order to improve impact resistance and vibration proof thereby to prevent the substrate from being damaged by impact or vibration.
Since fused salt is adhered to the chemically strengthened glass substrate, a cleaning process is also performed. Hitherto, the glass substrate for the magnetic disk after the chemical strengthening treatment is cleaned by using, for example, as described in Japanese Patent Application Laid-Open Hei 2-285508, alkaline cleaning agent, pure water, organic solvent, and the like.
In association with increase in recording density of the magnetic disk, a distance (spacing) between the magnetic disk and the magnetic head is requested to be narrowed more and more. It is, therefore, an urgent subject to completely remove foreign matters on the glass substrate which cause projections on the surface of the magnetic disk.
Although changes in quality (Dimming, Staining, Surface Deterioration, Chemical Durability, Chemical Durability to water and the like) of the surface of the glass substrate occurring before and after formation of a magnetic film or the like on the glass substrate also depend on surface cleanliness by the cleaning process and outer atmosphere, they have close relation with the kind and concentration of ion in the surface layer of the glass substrate. They exert influences on weather resistance and the life under operation environment of the magnetic disk and the reliability of the magnetic disk.
Although a predetermined cleaning effect can be obtained by the above-mentioned conventional cleaning treatment, even if the cleaning treatment is especially performed to the glass substrate withdrawn from the chemical strengthening treatment liquid, it is difficult to completely remove precipitated fused salt remained on the glass substrate.
The conventional cleaning treatment is insufficient to prevent the changes in quality of the glass surface such as burning and the like at a high level.